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[v2,2/8] bpf: allow helpers to return PTR_TO_SOCK_COMMON

Message ID 20190314113954.10210-3-lmb@cloudflare.com
State Deferred
Delegated to: BPF Maintainers
Headers show
Series Allow checking SYN cookies from XDP and tc cls act | expand

Commit Message

Lorenz Bauer March 14, 2019, 11:39 a.m. UTC 
It's currently not possible to access timewait or request sockets
from eBPF, since there is no way to return a PTR_TO_SOCK_COMMON
from a helper. Introduce RET_PTR_TO_SOCK_COMMON to enable this
behaviour.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
 include/linux/bpf.h   | 1 +
 kernel/bpf/verifier.c | 4 ++++
 2 files changed, 5 insertions(+)
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Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f02367faa58d..f62897198844 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -205,6 +205,7 @@  enum bpf_return_type {
 	RET_PTR_TO_MAP_VALUE_OR_NULL,	/* returns a pointer to map elem value or NULL */
 	RET_PTR_TO_SOCKET_OR_NULL,	/* returns a pointer to a socket or NULL */
 	RET_PTR_TO_TCP_SOCK_OR_NULL,	/* returns a pointer to a tcp_sock or NULL */
+	RET_PTR_TO_SOCK_COMMON_OR_NULL,	/* returns a pointer to a sock_common or NULL */
 };
 
 /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a52e723c8e5d..f60d9df4e00a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3148,6 +3148,10 @@  static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
 		regs[BPF_REG_0].id = ++env->id_gen;
+	} else if (fn->ret_type == RET_PTR_TO_SOCK_COMMON_OR_NULL) {
+		mark_reg_known_zero(env, regs, BPF_REG_0);
+		regs[BPF_REG_0].type = PTR_TO_SOCK_COMMON_OR_NULL;
+		regs[BPF_REG_0].id = ++env->id_gen;
 	} else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;